This invention relates to a gas-insulated switchgear and, more particularly, to a bushing for a gas-insulated switchgear for the connection to the insulated bus conductors of the electric power system for example.
FIG. 5 illustrates a conventional gas-insulated switchgear disclosed in Japanese Patent Laid-Open No. 6-12948. In this gas-insulated switchgear, disposed within a hermetic vessel 2 filled with an electrically insulating gas are interrupters 5 and a vessel wall of the hermetic vessel 2 has mounted thereon bushings 8 for electrically connecting the interrupters 5 to insulated bus conductors 13. The bushings 8 are disposed in parallel to each other and extend through the vessel wall of the hermetic vessel 2 and are connected to the interrupters 5 by means of elongated conductors 17 within the hermetic vessel 2.
FIG. 6 illustrates another conventional gas-insulated switchgear disclosed in Japanese Utility Model Laid-Open No. 5-23711. In this gas-insulated switchgear, a hermetic vessel 2 in which an electrically insulating gas is filled has contained therein disconnectors 4 and interrupters 5 and three insulated bus conductors 13 are electrically connected to the interrupters 5 through bushings 8 mounted to the vessel wall of the hermetic vessel 2. The bushings 8 have different configurations from each other and extend through the vessel wall of the hermetic vessel 2 to be connected to contacts 9 of the disconnectors 4 disposed in alignment on a common axis within the hermetic vessel 2.
According to the above-described conventional gas-insulated switchgear, for the gas-insulated switchgear shown in FIG. 5, a large space is needed for accommodating the elongated electric conductors 17 extending from the tip of the bushing 8, resulting in a large hermetic vessel 2. Also, for the gas-insulated switchgear shown in FIG. 6, different bushings of different configurations must be used to position the tips of the bushings 8 in alignment with the common axis, thus posing disadvantages that the gas-insulated switchgear is large-sized, installation area is large and that the product price is high.
Accordingly, the main object of the present invention is to provide a gas-insulated switchgear free from the above-discussed problems.
Another object of the present invention is to provide a gas-insulated switchgear that is small-sized, the bushings for each phase are the same and that the mechanical strength of the hermetic vessel can be improved.
With the above objects in view, the present invention resides in a gas-insulated switchgear comprising electric devices disposed in parallel to have a common axis for each phase for opening and closing electric circuits, a hermetic vessel containing the electric devices and filled with an electrically insulating gas and bushings mounted to and passing through a vessel wall of the hermetic vessel and each having an outer end connected to an insulated bus conductor at the outside of the hermetic vessel and an inner end connected to the electric device with the hermetic vessel. Each of the bushings has a central axis that is perpendicular to the common axis of the electric device and spaced apart from each other in the direction of extension of the common axis and shifted by a predetermined angle with respect to each other about the common axis.
The vessel walls of the hermetic vessel to which the bushings are mounted may be flat and may have a portion that extends at an angle from an inside position to an outside position with respect to other portion of the vessel wall so that the central axis of the bushings define predetermined angles therebetween that correspond to the predetermined angle of the central axis of the bushings.
The inner ends of the bushings mounted to the hermetic vessel may be positioned on said common axis.
The inner ends of the bushings may have mounted thereon contacts of the disconnectors.